Arm safe device for artillery projectiles

ABSTRACT

An electrical normally open single pole single throw switch for safing and arming projectiles has a forward terminal means, a hollow insulator proximately fixed to the forward terminal means and concentric therewith, a rear terminal means proximately fixed to the other end of the insulator and axially aligned therewith, an electrically conducting cantilever pole means having one end concentric with and fixed to the rear terminal, and a free end extending longitudinally toward and into the forward terminal means, an interlocking pole restraining means is axially mounted on the cantilever pole means intermediate to the free end and fixed end of the cantilever pole means. The interlocking pole restraining means is sequentially responsive only to first a linear accelerating force followed by an angular accelerating force. This combination of linear and angular accelerating forces, which are present in the normal launch of an artillery projectile, affect the switch closure thereby changing the projectile from a safe position to an arm position. Whenever the projectile experiences a decay in angular acceleration or spin the interlocking pole restraining means will open the electric switch and place the projectile once again in the safe mode.

United States Patent [191 Wagnecz Apr. 10, 1973 [541 ARM SAFE DEVICE FOR ARTILLERY PROJECTILES [5 7] ABSTRACT 5] lnvenlofi AkXalldel g Mine Hill, An electrical normally open single pole single throw switch for safing and arming projectiles has a forward [73] Assisnee: The United States of America as terminal means, a hollow insulator proximately fixed represented by the Secretary of he to the forward terminal means and concentric Army therewith, a rear terminal means proximately fixed to the other end of the insulator and axially aligned [221 F'led: July 1971 therewith, an electrically conducting cantilever pole [21 A N 166,146 means having one end concentric with and fixed to the rear terminal, and a free end extending longitudinally toward and into the forward terminal means, an inter- [58] Field of Search ..102/70.2 so 76 canmeve pole means. mermediate end ZOO/61.45 6146 3 1 and fixed end of the cantilever pole means. The interlocking pole restraining means is sequentially respon- [56] References Cited sive only to first a linear accelerating force followed by an angular accelerating force. This combination of UNITED STATES PATENTS linear and angular accelerating forces, which are 3 501 604 3 1970 Crockett ..200/61.45 R present in the normal launch of artillery projectile 2:938:46l 5/1960 film/702 R affect the switch closure thereby changing the projec- 3001043 9/ 1961 Evans I I I 102/30 X tile from a safe position to an arm position. Whenever 3,181,466 5/1965 Czavkowski". 102/702 R the projectile experiences a decay in angular accelera- 3,649,787 3/1972 Kasa ia A i 00/ 5 R tion or spin the interlocking pole restraining means 3,657,500 4/1972 Gawlick et al. ..200/6l.45 R will open the electric switch and place the projectile once again in the safe mode.

2 Claims, 5 Drawing Figures PATEHTEHAPR 1 01973 SHEET 1 0F 2;

FIG.

INVENTOR.

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ALEXANDER G. WAGNECZ a 9nd, ,M M M Y m-Ma PATEPHED Y BB 3,726,227

sum 3 OF 3 18 so I FIG. 5

INVENTOR. ALEXANDER G. WAGNECZ BYW zwJgKJ mfg wwau m,

ARM SAFE DEVICE FOR ARTILLERY PROJEC'IILES The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION Various mechanical and electrical means are known for making a projectile relatively safe to handle during the pre-launch phase, for arming the projectile or missile after it has left the launch vehicle, and for disarming the projectile in the event that it should malfunction. Some of the prior art devices utilize the linear acceleration of the projectile and the inertial mass of a member in a safe-arm device to perform a mechanical operation or to effect an electric switch closure. Other devices use the spin force of the projectile to cause a centrifugal sensitive member to perform a mechanical function and/or an electrical function. Some of these prior art devices have utilized a combination of both the linear acceleration and the angular acceleration of the spin given to the projectile to separately operate means responsive to each of these forces to unarm and arm the projectile during the various stages of projectile handling and delivery. All of the prior art devices fail to combine in one elemental means of the arm-safe mechanisms responsiveness to both linear and angular acceleration in a simple, small, reliable device.

Prior art devices are generally less satisfactory than the present invention because of their larger size, having larger number of parts to accomplish similar function, and are more costly and less reliable because of their greater complexity.

The present device provides a reliable means for' electrically arming and safing a projectile. The device is unique in that two interlocking inertial masses are required to function in sequence to achieve an electrical switch closure and arming. The device is positioned in the projectile so that its longitudinal axis is parallel to the longitudinal axis of the missile, with forward end pointed in the direction of the missile flight.

SUMMARY OF THE INVENTION The present invention relates to an electric, safearm-safe, normally open, single pole, single throw switch, whose pole piece will effect closure only when there is a combined sequentially imposed linear and angular accelerating force.

In accordance with the present invention a hollow cylindrical insulator has a conducting first forward end cap terminal fixedly attached thereto in one end and a conducting second rear end cap terminal fixedly attached in the other end. The first forward end cap terminal has a central bore coaxially aligned with the longitudinal axis of the cylindrical insulator. The second rear end cap terminal has a central bore coaxial with the cylindrical insulator, and locates and fixedly retains a spring wire therein in cantilever fashion. The other free end of the spring cantilever wire has attached thereto a contact. The contact has a central bore therein which is also concentric with the longitudinal axis of the cylindrical insulator. A setback insulatorweight assembly is held intermediately disposed to the contact and the second end cap inner surface when there are insufficient setback forces by a helically biased spring. The setback weight is fixedly held in a setback insulator bore by a pressed fit. The setback weight bore is made larger in diameter than the diameter of the cantilever spring wire so that the former can slidably move toward the second rear end cap when setback forces are present. The diameter of the setback insulator is smaller in diameter than the first end cap bore but larger in diameter than the outside cylindrical surface of the contact.

The sensitivity of the device to linear acceleration can be varied by changing the diameter and material of the biased helical spring, the weight of the insulator weight assembly and the amount of pre-stress compression put on the helical spring. The sensitivity of the device to angular acceleration or spin can be varied by changing the length, diameter, and material of the cantilever spring wire and the weight of the contact.

One of the objects of this invention is to provide two interlocking inertial masses which are required to function in sequence to achieve switch closure and arming.

Another object of this invention is to provide a normally open, single pole, single throw electrical switch which will not close until the device is subject to first a minimum linear acceleration and then to a subsequent angular acceleration.

Another object of this invention is to provide a normally open, single pole, single throw electrical switch which will positively open the switch whenever the angular accelerating forces in a projectile are no longer present, thereby making the projectile safe to remove in the event of a malfunction.

Another object of this invention is to provide a small size electrical switch which is suitable for projectiles with severe space limitations which require arm and safe operations.

Another object of this invention is to insure reliable operation by simplicity of construction of a safe and arm electrical switch sensitive only to sequential linear and angular accelerating forces.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the arm-safe electrical switch in the safe position taken along a radial plane through the longitudinal axis.

FIG. 2 is a cross-sectional view of FIG. 1 taken in the direction of line 22.

FIG. 3 is a cross-sectional view of FIG. 1 taken in the direction of line 3-3.

FIG. 4 is a cross-sectional view of FIG. 1 taken in the direction of line 44.

FIG. 5 is a cross-sectional view of the arm-safe electric switch in the armed position taken along a radial plane through the longitudinal axis.

- Throughout the following description like reference numerals are used to denote like parts of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is concerned with a device which will reliably effect the closure of a normally open single pole single throw switch only when it is subjected sequentially first to a preset minimum linear accelerating force followed by a subsequent preset minimum angular accelerating force which one normally finds in spin oriented projectiles. In its broader aspects it is intended to cover the switching of an electrical circuit for arming of a warhead in a missile only after the missile has been fired and for positively and automatically disarming the projectile so that it may be safely disposed of in the event that, for any reason, it fails to explode.

Referring now to FIG. 1, a forward end cap 10, made of conducting material such as brass, is press fit into one en'dof a cylindrical insulator 30. A rear end cap 20, also made of similar conducting material, is press fit into the other end of the cylindrical body insulator 30. The forward end cap has a forward end cap terminal 11 to which an electrical conductor (not shown) can readily be affixed, a shoulder 12 locates the position of the cap in the cylindrical insulator 30; in a similar manner the rear end cap has a rear end cap terminal 21 and a shoulder 22. The forward end cap 10 has a central bore 16 which is coaxial with the longitudinal axis of the cylindrical body insulator 30. The outer wall surface 14 interfitably engages the cylindrical body insulator inner wall 32. In a similar manner as aforedescribed the rear end cap outer wall 24 interfitably engages the inner wall 32 of the cylindrical insulator 30. The rear end cap 20 has a central bore 26 whose longitudinal axis is coaxial with the longitudinal axis of the cylindrical insulator 30. A spring wire 40 has a fixed end 42 positioned in the rear end cap bore 26 and a free end 44 extending in cantilever'construction into the forward end cap central bore 16. A cylindrical contact 50 has an outer wall surface 51 of smaller diameter thanthe forward end cap bore 16. Contact 50 has a concentric contact bore 52 which is press fit over the other end 44 of the spring wire 40. In the safe position of the device, that is when there is no linear and angular accelerating forces being applied, an insulatorweight assembly 60 is biasedly positioned intermediate to the contact 50 and the rear end cap 20 by a helical spring 80. The insulator-weight assembly 60-consists of two concentric hollow cylinders press fit together. A setback insulator outer cylinder surface 61 is smaller in diameter than the central bore 16 of the forward end cap 10 but larger in diameter than the outer surface 51 of contact 50 so that contact 50 is electrically isolated from the forward end cap 10 by a clearance space 53 whenever the insulator-weight assembly 60 is in the position shown in FIG. 1. The setback insulator inner wall 62 interfitably engages the setback weight 70. The setback weight 70 has ,a central bore 72 which is larger in diameter than the spring wire 40. When the device is subject to a linear accelerating force which overcomes the compression force of the helical spring 80 the insulator-weight assembly will slidably move toward the rear end cap. The helical spring 80 has one end 81 proximate to the inner surface 28 of the rear end cap 20 and the other end 82 proximate to the setback weight cylinder end 73.

FIG. 2 shows the circular configuration of the forward end cap terminal 11 and the forward end cap shoulder 12.

FIG. 3 illustrates the concentric relationship between the cylindrical insulator 30, the forward end cap 10, the contact 50 and the spring wire 40. In the safe configuration, where neither linear nor angular accelerating forces are being exerted, a clearance space 53 separates and electrically isolates contact 50 from the forward end cap 10.

FIG. 4 shows the concentric relationship between the cylindrical insulator 30, the helical spring and the spring wire 40 when the device is viewed in a direction looking toward the rear end cap inner surface 28 along line 4-4 as shown in FIG. 1.

FIG. 5 shows the arm-safe device in the armed position. In the armed position both linear and angular accelerating forces have sequentially acted upon the device, a residual angular acceleration is present due to the projectile spin. Under these conditions the helical spring 80 will be compressed by the insulator-weight assembly 60 so that the insulator-weight assembly 60 is below the forward end cap inner surface 18. The residual spin forces of the projectile will cause the pendulous mass consisting of the contact 50, the insulatorweight assembly 60, the helical spring 80 and the unsupported free end 44 of the spring wire 40 to bend so that the contact outer surface 51 touches the forward end cap central bore 16 thereby effecting a switch closure. When the device is in the aforementioned arm position a decrease in linear acceleration will not cause the switch to open as long as the centrifugal forces of spin are present.

In operation the device is positioned so that its longitudinal axis is parallel to the longitudinal axis of the projectile, and as the projectile experiences acceleration along its longitudinal axis in the gun barrel, the insulator-weight assembly 60 moves toward the rear end cap terminal 20 compressing the biased helical setback spring 80 against the rear end cap inner surface 28. The longitudinal movement of the insulator-weight setback assembly 60 enables the transverse movement of the contact 50 toward the forward end cap terminal bore 16. As the projectile travels down the gun barrel, spin about the projectile axis increases, at a minimum threshold level the contact 50 moves transversely towards and makes contact with the forward end cap bore 16 by bending spring wire 40. Projectile spin keeps the contact 50 against the forward end cap 10. When the projectile acceleration along its longitudinal axis decreases, the insulator-weight assembly is pushed toward the forwardend cap 10 by the biased helical spring 80 and comes to rest against the forward end cap inner surface 18 thereby keeping the device in the actuated or armed position as shown in FIG. 5. In the actuated condition electrical continuity is through the forward end cap 10, the contact 50, the spring wire 40, and the rear end cap 20. Abnormal decay of the projectile spin and consequent reduction in centrifugal force permits the contact 50 to move transversely away from the forward end cap 10 thereby opening the electrical circuit and permitting the insulator-weight setback assembly to re-enter the forward end cap bore 16. The device must undergo another repeat set of gun launch environment in order to rearrn.

I wish it to be understood that I do not desire to be limited to the exact detail of construction shown and described for obvious modifications will occur to a person skilled in the art.

What is claimed is:

1. An electrical normally open single pole single and throw switch for safing and arming projectiles which interlocking pole restraining means axially mounted comprises: on said cantilever pole means intermediate to said forward hollow terminal means which includes; free end of said cantilever pole means and fixed a cylindrical conducting forward end cap having a 5 end, sequentially responsive to a linear and anguclosed end and an open end, said forward end lar accelerating forces for effecting a switch clocap having a central bore said central bore axisure between said pole means and said forward terally aligned with said longitudinal axis of said minal and arming said projectile, and opening said hollow insulator switch and thereby safing said projectile when said a hollow cylindrical insulator having a first and 10 angular accelerating force has decayed.

second open end, said first end proximately fixed v 2. An electrical device as recited in claim 1 wherein to said forward terminal means and axially aligned Said kin g pole restraining comprises: therewith; a setback insulator-weight assembly having an outer rear terminal means proximately fixed to said second Setback insulator Sleeve and a inn r t a k open insulator end whi hin l de weight fixedly held within said insulator sleeve, a li d i l d ti rear d cap h i a rear said setback weight having a central bore which is end cap bore for fixedly positioning therein said g in diameter than Said Spring wife, said cantilever pole means, said rear end cap bore i back insulator sleeve having an outside diameter axially aligned with the longitudinal axis of said intermediate to Said forward end p central bore h ll insulator d i f d end cap Gem and said cylindrical contact surface, said setback b assembly operatively positioned intermediate said cantilever pole means having a fixed end concentric Contact and Said rear end p for movement along with said insulator and fixedly attached to said rear Said p g Wire; and terminal means, and its free end extending toward a helical Spring operatively Positioned Over Said and into Said f d terminal means which spring wire between said setback insulator-weight l assembly and said rear end cap for providing a aspring wire; compressive force against said assembly whereby a cylindrical contact fixedly attached to said spring Sald electrical swltch remam m an Open Safe,

free end, operatively positioned concentric with Posmon P to Setback forcesaid spring wire, for providing a contact surface; 

1. An electrical normally open single pole single throw switch for safing and arming projectiles which comprises: forward hollow terminal means which includes; a cylindrical conducting forward end cap having a closed end and an open end, said forward end cap having a central bore said central bore axially aligned with said longitudinal axis of said hollow insulator a hollow cylindrical insulator having a first and second open end, said first end proximately fixed to said forward terminal means and axially aligned therewith; rear terminal means proximately fixed to said second open insulator end which includes; a cylindrical conducting rear end cap having a rear end cap bore for fixedly positioning therein said cantilever pole means, said rear end cap bore is axially aligned with the longitudinal axis of said hollow insulator and said forward end cap central bore; cantilever pole means having A fixed end concentric with said insulator and fixedly attached to said rear terminal means, and its free end extending toward and into said forward terminal means which includes; a spring wire; a cylindrical contact fixedly attached to said spring free end, operatively positioned concentric with said spring wire, for providing a contact surface; and interlocking pole restraining means axially mounted on said cantilever pole means intermediate to said free end of said cantilever pole means and fixed end, sequentially responsive to a linear and angular accelerating forces for effecting a switch closure between said pole means and said forward terminal and arming said projectile, and opening said switch and thereby safing said projectile when said angular accelerating force has decayed.
 2. An electrical device as recited in claim 1 wherein said interlocking pole restraining comprises: a setback insulator-weight assembly having an outer setback insulator sleeve and an inner setback weight fixedly held within said insulator sleeve, said setback weight having a central bore which is larger in diameter than said spring wire, said setback insulator sleeve having an outside diameter intermediate to said forward end cap central bore and said cylindrical contact surface, said setback assembly operatively positioned intermediate said contact and said rear end cap, for movement along said spring wire; and a helical spring operatively positioned over said spring wire between said setback insulator-weight assembly and said rear end cap for providing a compressive force against said assembly whereby said electrical switch will remain in an open, safe, position prior to setback force. 